Users perceive an image-information processed by an information-processing device through the display device.
A liquid crystal display (LCD) device, which is one of the display devices, displays an image-information using liquid crystal of which transmissivity is changed according to the electric field applied the liquid crystal.
The liquid crystal regulates only the transmissivity. Therefore, a light source is needed so as to display an image.
A lamp is used as a light source. For example, a cold cathode fluorescent lamp (CCFL) is used as a lamp for supplying a liquid crystal display panel of the liquid crystal display device with light.
The cold cathode fluorescent lamp has many merits. For example, the cold cathode fluorescent lamp may have a cylindrical shape having a small diameter. The cold cathode fluorescent lamp generates white light that is similar to the solar light. The cold cathode fluorescent lamp has a long life span. The cold cathode fluorescent lamp generates a small amount of heat.
The cold cathode fluorescent lamp may be arranged variously according to a size of the liquid crystal display device.
In a small sized or in a middle sized liquid crystal display device, one or two cold cathode fluorescent lamps may be disposed adjacent to the side of a light guide plate (LGP), because one or two cold cathode fluorescent lamps provide the liquid crystal display panel with enough light to display an image. The liquid crystal display device described above is referred to as an edge-illumination type liquid crystal display device.
Comparatively, in a large sized liquid crystal display device, more than three cold cathode fluorescent lamps are needed so as to provide the liquid crystal display panel with enough light. In a large sized liquid crystal display device, cold cathode fluorescent lamps are arranged parallel with each other. The cold cathode fluorescent lamps are disposed under the liquid crystal display panel so as to apply light to the liquid crystal display panel. This liquid crystal display device is referred to as a direct-illumination type liquid crystal display device.
Nowadays, a size of a display panel becomes larger. Therefore, a length of the cold cathode fluorescent lamp also becomes longer. When the length of the cold cathode fluorescent lamp becomes longer, the cold cathode fluorescent lamp sags due to a weight thereof. When the cold cathode fluorescent lamp sags, the cold cathode fluorescent lamp provides the liquid crystal display panel with non-uniform light. Therefore, the display quality of the liquid crystal display device is deteriorated.